Adjustable thermal limit switch



Aug. 24V, 1948. H, ULANET 2,447,622

ADJUSTABLE THERMAL LIMIT SWITCH Filed Jan. 9. 1946 A INVENTOR ffymz www j Patented-ug. 24, 1948 UNITED s'rATEsPATENT OFFICE 2,447,622 ADJUSTABLE THERMAL Lnm'r swrcn Herman Ulanet, Newark, N. J.

Application January 9, 1946, SerialfNo. 840,058

This invention relates to improvements in ad- .instable electrical switches of the thermal limit type adapted to automatically open when tem perature o! a device or at a location served thereby exceeds a selected limit to which the switch is adjusted.

The invention has for an object to provide a novel electrical switch including a pair oi' relatively movable contact devices one of which comprises a bi-metallic element which is responsive to temperature rise, and manipulatable means operable to engage and disengage said contact devices to manually close and open the switch. and also adapted to relatively adjust said contact devices in switch closing engagement subject to be automatically opened by the response o! said blmetallic element to temperature oi a 1 selected predetermined degree.

The invention has for another object to provide a novel switch, characterized as above stated, wherein the contact device opposed to that comprlsing the loi-metallic element consists in a resilient contact arm, said switch having a stationary support above said resilient contact arm, a rotative control cam `iournaled in said support and adapted to operatively engage said resilient contact arm, and means to actuate said cam.

Other objects oi this invention, not at this time more particularly enumerated, will be understood trom the following detailed 'description of the saine.

An illustrative embodiment ci this invention is shown in the accompanying drawings, in which:

Fig. i is an elevational view of the manipular. ing means ci an adjustable thermal limit switch according to this invention; Fig. 2 is a sectional view, taken online 2-2 in Fig. but showing the switch in top pian elevation; Fig. 3 is a vertical longitudinal sectional view, taken on line 3--3 in 2, the switch being shown in ope'nor od condition; Fig. is a sectional view, taken on iine in 2, but showing the switch is adjusted closed or on :condition: and Fig. 5 is a transverse vertical sectional view, taken on line E- in. Fig.

Similar characters oi? reference are employed in the hereinabove described views, to indicate corresponding parts.

The switch structure oi this invention comn prises a stationary supporting plate l0 having a butt portion I I integral therewith. Said supporting plate l0 is of rigid inflexible character, and, to assure such rigidity, is provided with means to stillen the same against bending, such e. g. as stiiening flanges or ribs I2 disposed to project 1 Claim. (Cl. 20D- 138) aligned; periorate bearing ears I3. the purpose oi' which will be hereinafter disclosed.

Underlying said supporting plate Il, in suitably spaced apart relation thereto, is an electrically conductive resilient contact arm I4 having a butt portion il which underlies the butt portion II of said supporting plate l0.` Super-posed upon said butt portion I8 of said contact arm IQ. so as to be in electrical contact therewith. is a pole piece Il. Said pole piece VI8 is provided with an exteriorly extending angular binding post lug l1. through which is threaded e, binding screw yI8 operative to mechanically and electrically connect thereto. and thus to said pole piece Il and contact arm il, a conductor i@ comprising one side oi an electrical circuit desired to be controlled by the switch.

Underlying said contact arm'A il, in suitably spaced apart relation thereto is an, electrically conductive iii-metallic element 20 which con stitutes the thermostatic or thermoresponsive member of the'switch. Said loi-metallic element 2c is also provided with a loutt portieri il which underlies the butt portion lo oi said contact arm is. Superposed upon said butt portion 2i of said ici-metallic element t, so as to he in electrical contact therewith, is another pole piece 2d, which islprcvided with an exterioriy extending angular binding post lug Eil. through which is threaded a binding screw Qil operative to mechanically and electrically connect theretoD and thus to the pole piece 22 and loi-metallic element di?, e, conductor comprising the opposite side oi the electrical circuit to ce controlled icy 'the switch.

interposed between the butt portion li ci the supporting plate l@ and the underlying engaged pcie piece itl and hatt portion i5 oi' the contact arm irl is a separator piece or plate 25 of suitable electr-loci insulation material. En like mennen interposed between the butt portion iii of the Contact arm '.l and the underlying engaged pole piece and butt portion iii ci the loi-metaliic element 2o is a similar separator piece or plate 2li oi suitable electrical 'insulation material. Undera lying the butt portion 2i ci said loi-metallic element 20 is another piece or plate 28 oi' suitable electrical insulation material.

To secure the butt portions of the described lswitch parts and associated electrical insulation material in assembled relation. and thereby said switch parts in cooperative relation, suitable .fastening means is passed through the assembly.

A, preferable form of fastening means comprises one or more hollow rivets 29, the same being insulated from electrical contact with the conductive parts of the switch by surrounding sleeves il@ of electrical insulation material. Said hollow rivets 29 provide passages through which may be passed fastening screws ti, whereby to secure the butt or heel of the switch to a support t2 provided in connection with the device or at the location to be served by the switch.

Said contact arm il i's provided, adjacent to its free end to project from its under face, with a contact element 33. In like manner, said bimetallic element 20 is provided, adjacent to its free end to project from its upper face, with a similar contact element 3i adapted to be engaged by said contact element 33 oi the contact arm i4, whereby to bring said contact arm and bi' metallic element into circuit completing relation when the switch is closed.

Said resilient contact arm id is biased by its inherent tension so as to be yieldably urged away from the bi-metallic element 2@ and toward the supporting plate iii.

Journaled in and between the bearing ears i8 oi the supporting plate i is a rotatable shaft 55 of suitable length. Ailixed to said shaft t5, so as to be turnable thereby, is a control cam 36. Said supporting plate ill is provided with a slot 3l through which the `periphery of the cam tt extends so as to be directly opposed to the underlying resilient contact arm it. The periphery of said cam 36 is provided with a low section 38 of preferably straight or flat conformation, and

a high section 39, leading from saidlow section, which is of progressively increasing radius. The resilient contact arm itl is provided with an abutment stud t0, electrically insulated therefrom by suitably arranged insulation material 4i. Said abutment stud d@ is opposed to and is engaged by the cam 3S.l Due toits bias toward the supporting plate it" and cam St, the resilient contact arm ie is yieidably urged against the latter. When the cam is positioned to 0ppose its low section 38 to the abutment stud 4d, the contact arm it will be moved by its tensional bias away from the bi-metallic element 2U, and thus to switch open or o position (see Fig).

Auixed to an exterior end of said cam shaft 35 is a ilnger piece t2 for rotatively actuating the cam 36. This finger piece l2 includes an indicator projection orpointer piece tit which is adapted to cooperate with an adjaoently located and suitably xed scale iiivcalibrated to indicate positions of the control cam which condition the switch for thermal limit operation when influenced by selected temperature conditions. as e. g. by low heat, medium heat or high heat within a desired range of minimum and maximum temperature for which a givenswitch is designed to respond.

In the use of the switch, by turning the control cam 36 in clockwise direction, the low section 38 is moved away from the abutment stud 40 of the resilient contact arm id, and the high section 39 of said cam is moved toward the latter, thereby depressing the resilient contact arm i4, against its tenslonal stress, and thus swing down thesame so that its contact element 33 engages the contact element 34 of the bi-metallic element 20, and thereby closes the switch (see Fig. 4).

A For operative circuit breaking response of the bimetallic element to relatively low temperature,

turning ci the cam @il is limited to an amount which is sumcient to bring the contact elements 33 and 3G together, with substantially little downward deection of the lol-metallic element 2u (see Fig. e). When the switch is thus closed, upon a, desired minimum rise oi temperature effective upon the loi-metallic element 2d, the latter will be downwardly warped, whereby to promptly separate the contact element 3Q from the contact element tt. thus automatically opening the switch to interrupt the circuit controlled thereby (see broken line delineation oi the bimetallic element shown in Fig, 4l, until a sufilcicnt drop in inuencing temperature occurs, whereby to permit said loi-metallic element 2d to contract to normal condition, and thereby again automatically close the switch.

By turning the cam 38 beyond mere switch closing position, the degree of down swing of the resilient contact arm it is increased to an extent sufllcient' to produce an accompanying downward exing of the bi-metallic element 2t. Under such circumstances, initial heat induced warping of the bi-metallic element 2U will not separate the contacts 33 and 34 until such warping first balances the mechanical deflection of the bi-metallic element induced by the downward pressure oi the resilient contact arm I4, and then continues beyond such balance, whereupon the switch will automatically open. It will be obvious that under these circumstances a higher degree of temperature must influence the loi-metallic element before automatic 'opening of the switch by the latter will be effected. From this it will be understood that the more the cam 36 is advanced, whereby to increasingly depress the resilient contact arm it and mechanicallyydeect the loi-metallic element til, the higher will be the temperature required to in i'luence the bi-metallic element ior automatic switch opening eiect, until, by application of the high section 89 of the cam to the resilient contact arm and loi-metallic element, the switch will be conditioned to automatically open only when inuenced by a maximum degree ci temperature rise.

lilrom the above it will be apparent that a very simple and emcient adjustable thermal limit switch is. provided by the instant invention. I am aware that changes could be made in the above described switch structure without departing from the scope of this invention as defined .by the following claim. It is therefore intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim: in adjustable thermal limit switch comprisin an upper plate, a lower loi-metallic arm, and an intermediate flexible arm disposed. in spaced apart super-posed relation, the same having fixed end portions, vmeans to insulate said fixed end portions one from another, said plate having stiilening angesalong its side margins perpendicular to the Diane thereof, said ilanges including, at the free end portion of said plate, transversely aligned bearing ears, a rotatable transverse shaft journaled in said bearing ears, a cam on said shaft disposed to oppose said flex ible arm at a point intermediate its xed end portion and free end whereby to adjust the relation of said flexible arm to said bi-metallic arm, said flexible arm having an abutment stud aiilxed thereto in opposition to said cam. means to in- 5 sulate said abutment stud from flexible arm.

the free end portion of said flexible arm having a contact element. the free end o! said lei-metallic arm having a 'contact element opposed to the contact element-tof said iiexible arm, and said 5 flexible arm and said bi-metallic arm being each provided with means for connecting the same in an electrical circuit to be controlled by the switch.

HEMANULANET.

The following references are oi' record in the file oLthis patent:

UNITED STATES PATENTS Number Name l Date Wolcott et al. May 10, 1932 Kuhn et al. Dec. '18, 1934 Smith leb. 13, 1940 Siedle et al. June 4, 1940 Winning Apr. 7, 1942 De Lancey June I6, 1942 Ulanet June 8, 1943 

